The present invention relates generally to semiconductor integrated circuits. More particularly, it pertains to enhancing outputting capability of a Synchronous Dynamic Random Access Memory (SDRAM) so as to allow the SDRAM to be adaptively compatible with different termination requirements of various types of circuits.
Memory devices are integrated circuits in which information may be stored and from which information may be extracted when desired. Each memory device is built from a plurality of memory cells. Each memory cell memorizes a bit of data. Although a bit of data seems insignificant, it may determine whether the stored information is correct, such as an amount in a checking account.
The process of memorizing the bit of data by the memory cell is an example of the ingenuity of a memory device. But also equally important is the process of extracting the memorized bit of data from the memory cell. The process of extracting outputs the memorized bit of data so that subsequent devices, which are coupled to the memory device, may make use of it.
Certain devices require that the memory device powerfully drive the memorized bit of data from the memory device to the input of those certain devices. Yet other devices, especially those used in graphics products, require a less powerful drive of the memorized bit of data. Current memory devices are unable to adapt to the needs of various devices.
Thus, what is needed are devices and methods to adapt to the needs of various devices coupled to the memory device so as to enhance the output operations of future generations of memory devices, such as synchronous DRAMs (SDRAMs), and double-data-rate SDRAMs (DDR SDRAMs).
The above-mentioned problems with memory devices and other problems are addressed by the present invention and will be understood by reading and studying the following specification. Devices and methods are described which accord these benefits.
One illustrative embodiment includes an output driver having two modes of operation. The output driver includes a first circuit to support one of the two modes. One of the two modes drives a subsequent input stage of another circuit without a termination in between the output driver and the subsequent input stage of the other circuit. The output driver includes a second circuit to support the other of the two modes. The other of the two modes drives the subsequent input stage of the other circuit with the termination in between the output driver and the subsequent input stage of the other circuit.
Another illustrative embodiment includes an output driver for driving data at an output. The output driver includes a full-drive pull-up circuit to drive data high to a full level, a reduced-drive pull-up circuit to drive data high at a reduced level, a full-drive pull-down circuit to drive data low to a full level, and a reduced-drive pull-down circuit to drive data low at a reduced level.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver circuit that produces a mode selected from a group consisting of a full-drive mode and a reduced-drive mode. The circuit also includes an output driver coupled to the pre-driver circuit that outputs the data in accordance with the mode produced by the pre-driver circuit.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver circuit that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a negative protection circuit. The circuit includes an output driver coupled to the pre-driver circuit that outputs a data signal in accordance with the mode produced by the pre-driver circuit. The negative protection circuit inhibits undesired turning-on of the output driver.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a booting circuit that boots a boot-up signal to a voltage level. The voltage level is selected from a regular voltage supply level or a pumped voltage supply level. The circuit includes an output driver coupled to the pre-driver circuit that outputs a data signal in accordance with the mode produced by the pre-driver circuit.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver circuit that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a reduced-drive pull-up driver so as to produce the reduced-drive mode at a reduced-drive node.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver circuit that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a full-drive pull-up driver so as to produce the full-drive mode at a full-drive node. The circuit includes an output driver coupled to the pre-driver circuit that outputs a data signal in accordance with the mode produced by the pre-driver circuit.
Another illustrative embodiment includes a circuit to output data in a memory device. The circuit includes a pre-driver circuit that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a full-drive pull-down driver so as to produce the full-drive mode at a full-drive node. The circuit includes an output driver coupled to the pre-driver circuit that outputs a data signal in accordance with the mode produced by the pre-driver circuit.
Another illustrative embodiment includes a pre-driver circuit that produces a mode signal selected from a group consisting of a full-drive mode and a reduced-drive mode. The pre-driver circuit includes a reduced-drive pull-down driver so as to produce the reduced-drive mode at a reduced-drive node. The pre-driver circuit includes an output driver coupled to the pre-driver circuit that outputs a data signal in accordance with the mode produced by the pre-driver circuit.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.